For many years, automotive engineers, engine builders and mechanics have sought to increase the efficiency and performance of internal combustion engines. It is known that the length and shape of the runners that extend from the plenum (the area underneath the carburetor or fuel injection system) are very important to the overall efficiency and performance realized.
For example, in 1971, Edelbrock started one trend with its Tarantula manifold which used a small volume open chamber plenum manifold with small cross section runners. m Shortly thereafter, Weiand followed with its X-elerator manifold and in 1976 Holly introduced it Street Dominator line of manifolds. These manifolds have an open plenum design and the mixture velocity is quite high so that low and mid-range performance is close to that provided by the stock manifold, but at the same time considerably better power is provided at the top end or high RPM range. These manifolds create amazing power increases using only a four barrel carburetor.
The intake manifold is actually an extension of the intake ports on the carburetor and most of the fluid flow considerations that apply to head ports also apply to the manifold runners. It is important to view each manifold runner and head port as a separate leg of the dynamic flow system, and the path that the air/fuel mixture takes from the mouth of the manifold runner at the plenum to the combustion chamber should be, in a sense, considered as one.
Presently, virtually all performance manifolds are based on a large centrally located plenum with reasonably straight runners from the plenum to the port entries in the head. This configuration is commonly called an open plenum manifold. The biggest advantage of this configuration is that the common manifold under the carburetor allows each runner/cylinder to draw fuel from all four of the carburetor venturis (when using a four barrel carburetor) when the throttle is wide open. In effect, the partially vaporized air/fuel mixture exits the bottom of the carburetor venturis as four separate streams. As each cylinder draws on the plenum, the four streams (or portions of the streams) bend toward the appropriate runner entry and form a single stream, which then flows into the runner and feeds the cylinder. This allows each runner to draw a greater volume of the air/fuel mixture during the available induction period.
In a typical V-type engine arrangement using either a four barrel carburetor system or a two barrel center carburetor system, it is virtually impossible to make all of the runners in an open plenum manifold identical in length. The runners leading to the cylinders on the far comers of the engine will be longer and the runners leading to the cylinders at the center of the engine will be shorter. This means that the flow path to each of the cylinders will be different. For example, in a manifold layout typically used in the V-8 type engine, four cylinders will be fed with a long flow path and four cylinders will be fed with a short flow path. Thus, the biggest problem to overcome in an open plenum manifold design is finding ways to minimize these flow path differences.
Early open manifold designs were terrible in this regard. In some designs, the end cylinders ran very lean while the center cylinders ran very rich. Other designs that attempted to compensate for this problem ended up running the end cylinders rich and the center cylinders lean. The more recent designs from the engine manufacturers are much improved and work much better.
The most important aspect when using an open plenum manifold is to match up the open plenum manifold with the requirements of the particular engine being used. The engine will respond differently depending on the length, volume and contours of the manifold runners. A manifold with longer runners will produce better low RPM torque and power while a manifold with shorter runners will produce better top end torque and power.
One of the best ways to improve low and mid-range torque and power is to use a cross ram type manifold. This type of manifold uses two carburetors positioned in a transverse manner instead of in line with the engine. The carburetor positioned closest to the right bank of cylinders feeds the left bank of cylinders. The carburetor positioned closest to the left bank of cylinders feeds the right bank of cylinders. With this configuration, the runners can be made quite a bit longer with good results.
Notwithstanding the type of manifold being used, the mechanic who is trying to increase the performance, torque or efficiency of the engine is still faced with the problem that the runner lengths are fixed.
It is an object of the present invention to provide to provide the mechanic with the ability to vary the length of the runners so that the proper configuration can be selected to optimize the performance, torque or efficiency of whatever engine is being used.
It is a feature of the present invention that interchangeable runners are provided so that the mechanic can select the optimal runner length for each cylinder. The open plenum manifold has a compact design for quicker response from the engine. The base plates and block off plates on the top of the plenum offer the mechanic the option of using one, two or three two-barrel carburetors or one, two or three four-barrel carburetors or one, two or three fuel injection systems or more of either for special applications.
It is an advantage of the present invention that any V-type or I-type engine can be configured for the highest performance, torque or efficiency be simply selecting the number and type of carburetors or fuel injection systems and then selecting the proper runner lengths for each of the cylinders.
Other objects, features and advantages of the present invention will become apparent from a consideration of the following detailed description.